Pacemakers, defibrillators and implanted cardioverter defibrillators (“ICDs”) have been successfully implanted for years for treatment of heart rhythm conditions.
Pacemakers are implanted in patients who have bradycardia (slow heart rate). The pacemakers detect periods of bradycardia and deliver electrical stimuli to increase the heartbeat to an appropriate rate.
ICDs are implanted in patients who may suffer from episodes of fast and irregular heart rhythms called tachyarrhythmias. An ICD can cardiovert the heart by delivering electrical current directly to the heart to terminate an atrial or ventricular tachyarrhythmia, other than ventricular fibrillation. An ICD may alternatively defibrillate the heart in a patient who may suffer ventricular fibrillation (VF), a fast and irregular heart rhythm in the ventricles. During a VF episode, the heart quivers and can pump little or no blood to the body, potentially causing sudden death. An ICD implanted for correction of ventricular fibrillation will detect a VF episode and deliver an electrical shock to the heart to restore the heart's electrical coordination.
Another type of implantable defibrillation device treats patients who may suffer from atrial fibrillation (AF), which is a loss of electrical coordination in the heart's upper chambers (atria). During AF, blood in the atria may pool and clot, placing the patient at risk for stroke. An electrophysiological device implanted for correction of atrial fibrillation will detect an AF episode and deliver an electrical shock to the atria to restore electrical coordination.
Pacemakers and ICDs are routinely implanted in the pectoral region either under the skin (subcutaneous) or under the pectoral muscle. The leads are placed at appropriate locations within or on the heart. Because of this complexity, a cardiologist identifying a heart rhythm condition may be required to refer his or her patient to sub-specialists or surgeons for implantation of a pacemaker or ICD—thus delaying implantation of the device in a patient who urgently needs it. It is thus desirable to simplify these devices and the. procedures for implanting them so as to permit their implantation by a broader range of physicians.
U.S. application Ser. No. 10/453,971, filed Jun. 4, 2003, and Ser. No. 10/862,113, filed Jun. 4, 2004, describe intravascular systems that may be used to deliver electrical energy to the heart such as for defibrillation, pacing, and/or cardioversion of the heart. These applications are incorporated herein by reference for all purposes.
Generally speaking, the systems described in the '971 and '113 applications include at least one housing containing the necessary circuitry and related components, and optionally include at least one lead carrying the electrodes needed to deliver the electrical energy to the body. Some or all of these components are positioned within the vasculature, such as in the superior vena cava (“SVC”), the inferior vena cava (“IVC”), the left or right subclavian vein (“LSV” or “RSV”), coronary sinus and/or within other vessels in the venous or arterial system. For some of the implant components (such as the housing and/or lead), retention devices are needed to retain the implant within the vasculature.
The '971 and '113 applications sleeves or anchors that may be introduced after the implant to be retained has been positioned at a desired location within the vessel, or that may be introduced simultaneously with the implant. In some embodiments, the anchor is positioned adjacent the implant and expanded to a radially expanded position. During this expansion step the retention sleeve may self-expand and/or it may be expanded using an expansion tool such as a balloon passed into the retention sleeve's central lumen and subsequently inflated. When the retention sleeve is expanded, its radial forces engage the implant and secure the implant against the vessel wall. Blood flowing through the vessel passes through the tubular interior of the retention sleeve.
The '971 and '113 applications describe the retention devices as being either separate components from the implants they are intended to retain, or as being integral with the retained components. The present application is directed to alternative retention devices for supporting medical implants within blood vessels. Although the focus of this description is on retention devices that are integrated with the medical implants they retain, they are equally useful as components that are physically separate or separable from the medical implants. It should also be noted that although these retention devices will be described in the context of intravascular cardioverters, defibrillators, and or pacemakers, they are equally suitable for any type of medical implant that must be retained within a blood vessel.